Vol. 3A 7-27
MULTIPLE-PROCESSOR MANAGEMENT
7.8.1 State of the Logical Processors
The following features are part of the architectural state of logical processors within IA-32
processors supporting Hyper-Threading Technology. The features can be subdivided into three
groups:
• Duplicated for each logical processor
• Shared by logical processors in a physical processor
• Shared or duplicated, depending on the implementation
The following features are duplicated for each logical processor:
• General purpose registers (EAX, EBX, ECX, EDX, ESI, EDI, ESP, and EBP)
• Segment registers (CS, DS, SS, ES, FS, and GS)
• EFLAGS and EIP registers. Note that the CS and EIP registers for each logical processor
point to the instruction stream for the thread being executed by the logical processor.
• x87 FPU registers (ST0 through ST7, status word, control word, tag word, data operand
pointer, and instruction pointer)
• MMX registers (MM0 through MM7)
• XMM registers (XMM0 through XMM7) and the MXCSR register
• Control registers (CR0, CR2, CR3, CR4) and system table pointer registers (GDTR,
LDTR, IDTR, task register)
Figure 7-4. IA-32 Processor with Two Logical Processors Supporting HT Technology
Logical
Processor 0
Architectural
State
Bus Interface
Local APIC
Local APIC
Logical
Processor 1
Architectural
State
Execution Engine
System Bus
